From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E1341C433F5 for ; Thu, 23 Sep 2021 20:22:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF14861038 for ; Thu, 23 Sep 2021 20:22:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243083AbhIWUXc (ORCPT ); Thu, 23 Sep 2021 16:23:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:60434 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240613AbhIWUX3 (ORCPT ); Thu, 23 Sep 2021 16:23:29 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CFBA861019; Thu, 23 Sep 2021 20:21:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1632428517; bh=IR8y58oEGt27nadwVb9/vZbKRzoq0owCbMQOV/qJWao=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=RVL9Bsjzabh7A/Bbmmg5JGvSvtUZc/UBn2FjcvPMZ6Yz2oTE858z2euRzDTT4wEU/ Ks+tou+cYDs/qnlhy5KwGGRzQjW+wzgeTJaSsKvEj7pjpiSZ+QS8Vh+t2LyV/ruMOj 7RcanISQKk25ca/f4bgkAathlHl5vCaCU5/WivmdqhucpJaO3IhRieAVRBgX2dt1s5 Mu70nV6ZMxBQQPxcUVGswy5lo5r3PT1kEXzNS+qbEsQ+8h5/ebrvnd7oekCt0lybqf RQaDlr4gON/+EkoGdJ5qRjzHu/QCl81zi0wbgAqc5lnoYw4M/5GDLVv6oljQGuW9Or 1r2zmbbBOJIZA== Message-ID: <5aa9e385b38ce0f63d6b531ede2baafd17fc7861.camel@kernel.org> Subject: Re: [PATCH v6 1/7] x86/sgx: Provide indication of life-cycle of EPC pages From: Jarkko Sakkinen To: Tony Luck , Sean Christopherson , Dave Hansen Cc: Cathy Zhang , linux-sgx@vger.kernel.org Date: Thu, 23 Sep 2021 23:21:54 +0300 In-Reply-To: <20210922182123.200105-2-tony.luck@intel.com> References: <20210917213836.175138-1-tony.luck@intel.com> <20210922182123.200105-1-tony.luck@intel.com> <20210922182123.200105-2-tony.luck@intel.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.36.5-0ubuntu1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On Wed, 2021-09-22 at 11:21 -0700, Tony Luck wrote: > SGX EPC pages go through the following life cycle: >=20 > DIRTY ---> FREE ---> IN-USE --\ > ^ | > \-----------------/ >=20 > Recovery action for poison for a DIRTY or FREE page is simple. Just > make sure never to allocate the page. IN-USE pages need some extra > handling. >=20 > It would be good to use the sgx_epc_page->owner field as an indicator > of where an EPC page is currently in that cycle (owner !=3D NULL means > the EPC page is IN-USE). But there is one caller, sgx_alloc_va_page(), > that calls with NULL. >=20 > Since there are multiple uses of the "owner" field with different types > change the type of sgx_epc_page.owner to "void *. >=20 > Start epc_pages out with a non-NULL owner while they are in DIRTY state. >=20 > Fix up the one holdout to provide a non-NULL owner. >=20 > Refactor the allocation sequence so that changes to/from NULL > value happen together with adding/removing the epc_page from > a free list while the node->lock is held. >=20 > Signed-off-by: Tony Luck > --- > arch/x86/kernel/cpu/sgx/encl.c | 5 +++-- > arch/x86/kernel/cpu/sgx/encl.h | 2 +- > arch/x86/kernel/cpu/sgx/ioctl.c | 2 +- > arch/x86/kernel/cpu/sgx/main.c | 21 +++++++++++---------- > arch/x86/kernel/cpu/sgx/sgx.h | 4 ++-- > 5 files changed, 18 insertions(+), 16 deletions(-) >=20 > diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/enc= l.c > index 001808e3901c..62cf20d5fbf6 100644 > --- a/arch/x86/kernel/cpu/sgx/encl.c > +++ b/arch/x86/kernel/cpu/sgx/encl.c > @@ -667,6 +667,7 @@ int sgx_encl_test_and_clear_young(struct mm_struct *m= m, > =20 > /** > * sgx_alloc_va_page() - Allocate a Version Array (VA) page > + * @owner: struct sgx_va_page connected to this VA page > * > * Allocate a free EPC page and convert it to a Version Array (VA) page. > * > @@ -674,12 +675,12 @@ int sgx_encl_test_and_clear_young(struct mm_struct = *mm, > * a VA page, > * -errno otherwise > */ > -struct sgx_epc_page *sgx_alloc_va_page(void) > +struct sgx_epc_page *sgx_alloc_va_page(void *owner) > { > struct sgx_epc_page *epc_page; > int ret; > =20 > - epc_page =3D sgx_alloc_epc_page(NULL, true); > + epc_page =3D sgx_alloc_epc_page(owner, true); > if (IS_ERR(epc_page)) > return ERR_CAST(epc_page); > =20 > diff --git a/arch/x86/kernel/cpu/sgx/encl.h b/arch/x86/kernel/cpu/sgx/enc= l.h > index fec43ca65065..2a972bc9b2d1 100644 > --- a/arch/x86/kernel/cpu/sgx/encl.h > +++ b/arch/x86/kernel/cpu/sgx/encl.h > @@ -111,7 +111,7 @@ void sgx_encl_put_backing(struct sgx_backing *backing= , bool do_write); > int sgx_encl_test_and_clear_young(struct mm_struct *mm, > struct sgx_encl_page *page); > =20 > -struct sgx_epc_page *sgx_alloc_va_page(void); > +struct sgx_epc_page *sgx_alloc_va_page(void *owner); > unsigned int sgx_alloc_va_slot(struct sgx_va_page *va_page); > void sgx_free_va_slot(struct sgx_va_page *va_page, unsigned int offset); > bool sgx_va_page_full(struct sgx_va_page *va_page); > diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/io= ctl.c > index 83df20e3e633..655ce0bb069d 100644 > --- a/arch/x86/kernel/cpu/sgx/ioctl.c > +++ b/arch/x86/kernel/cpu/sgx/ioctl.c > @@ -30,7 +30,7 @@ static struct sgx_va_page *sgx_encl_grow(struct sgx_enc= l *encl) > if (!va_page) > return ERR_PTR(-ENOMEM); > =20 > - va_page->epc_page =3D sgx_alloc_va_page(); > + va_page->epc_page =3D sgx_alloc_va_page(va_page); > if (IS_ERR(va_page->epc_page)) { > err =3D ERR_CAST(va_page->epc_page); > kfree(va_page); > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/mai= n.c > index 63d3de02bbcc..69743709ec90 100644 > --- a/arch/x86/kernel/cpu/sgx/main.c > +++ b/arch/x86/kernel/cpu/sgx/main.c > @@ -457,7 +457,7 @@ static bool __init sgx_page_reclaimer_init(void) > return true; > } > =20 > -static struct sgx_epc_page *__sgx_alloc_epc_page_from_node(int nid) > +static struct sgx_epc_page *__sgx_alloc_epc_page_from_node(void *owner, = int nid) > { > struct sgx_numa_node *node =3D &sgx_numa_nodes[nid]; > struct sgx_epc_page *page =3D NULL; > @@ -471,6 +471,7 @@ static struct sgx_epc_page *__sgx_alloc_epc_page_from= _node(int nid) > =20 > page =3D list_first_entry(&node->free_page_list, struct sgx_epc_page, l= ist); > list_del_init(&page->list); > + page->owner =3D owner; > sgx_nr_free_pages--; > =20 > spin_unlock(&node->lock); > @@ -480,6 +481,7 @@ static struct sgx_epc_page *__sgx_alloc_epc_page_from= _node(int nid) > =20 > /** > * __sgx_alloc_epc_page() - Allocate an EPC page > + * @owner: the owner of the EPC page > * > * Iterate through NUMA nodes and reserve ia free EPC page to the caller= . Start > * from the NUMA node, where the caller is executing. > @@ -488,14 +490,14 @@ static struct sgx_epc_page *__sgx_alloc_epc_page_fr= om_node(int nid) > * - an EPC page: A borrowed EPC pages were available. > * - NULL: Out of EPC pages. > */ > -struct sgx_epc_page *__sgx_alloc_epc_page(void) > +struct sgx_epc_page *__sgx_alloc_epc_page(void *owner) > { > struct sgx_epc_page *page; > int nid_of_current =3D numa_node_id(); > int nid =3D nid_of_current; > =20 > if (node_isset(nid_of_current, sgx_numa_mask)) { > - page =3D __sgx_alloc_epc_page_from_node(nid_of_current); > + page =3D __sgx_alloc_epc_page_from_node(owner, nid_of_current); > if (page) > return page; > } > @@ -506,7 +508,7 @@ struct sgx_epc_page *__sgx_alloc_epc_page(void) > if (nid =3D=3D nid_of_current) > break; > =20 > - page =3D __sgx_alloc_epc_page_from_node(nid); > + page =3D __sgx_alloc_epc_page_from_node(owner, nid); > if (page) > return page; > } > @@ -559,7 +561,7 @@ int sgx_unmark_page_reclaimable(struct sgx_epc_page *= page) > =20 > /** > * sgx_alloc_epc_page() - Allocate an EPC page > - * @owner: the owner of the EPC page > + * @owner: per-caller page owner > * @reclaim: reclaim pages if necessary > * > * Iterate through EPC sections and borrow a free EPC page to the caller= . When a > @@ -579,11 +581,9 @@ struct sgx_epc_page *sgx_alloc_epc_page(void *owner,= bool reclaim) > struct sgx_epc_page *page; > =20 > for ( ; ; ) { > - page =3D __sgx_alloc_epc_page(); > - if (!IS_ERR(page)) { > - page->owner =3D owner; > + page =3D __sgx_alloc_epc_page(owner); > + if (!IS_ERR(page)) > break; > - } > =20 > if (list_empty(&sgx_active_page_list)) > return ERR_PTR(-ENOMEM); > @@ -624,6 +624,7 @@ void sgx_free_epc_page(struct sgx_epc_page *page) > =20 > spin_lock(&node->lock); > =20 > + page->owner =3D NULL; > list_add_tail(&page->list, &node->free_page_list); > sgx_nr_free_pages++; > =20 > @@ -652,7 +653,7 @@ static bool __init sgx_setup_epc_section(u64 phys_add= r, u64 size, > for (i =3D 0; i < nr_pages; i++) { > section->pages[i].section =3D index; > section->pages[i].flags =3D 0; > - section->pages[i].owner =3D NULL; > + section->pages[i].owner =3D (void *)-1; Probably should have a named constant. Anyway, I wonder why we want to do tricks with 'owner', when the struct has a flags field? Right now its use is so nice and straight forward, and most importantly intuitive. So what I would do instead of this, would be to add something like /* Pages, which are being tracked by the page reclaimer. */ #define SGX_EPC_PAGE_RECLAIMER_TRACKED BIT(0) /* Pages, which are allocated for use. */ #define SGX_EPC_PAGE_ALLOCATED BIT(1) This would be set by sgx_alloc_epc_page() and reset by sgx_free_epc_page(). In the subsequent patch you could then instead of /* * If there is no owner, then the page is on a free list. * Move it to the poison page list. */ if (!page->owner) { list_del(&page->list); list_add(&page->list, &sgx_poison_page_list); goto out; } you would /* * If there is no owner, then the page is on a free list. * Move it to the poison page list. */ if (!page->flags) { list_del(&page->list); list_add(&page->list, &sgx_poison_page_list); goto out; } You don't actually need to compare to that flag because the invariant would be that it is set, as long as the page is not explicitly freed. I think this is a better solution than in the patch set because it does not introduce any unorthodox use of anything. /Jarkko